The present application relates to communication techniques, and more particularly, but not exclusively, relates to wireless network communications techniques involving virtual full-duplex techniques called rapid on-off-division duplexing (referred to herein as RODD). These techniques find application in Mobile ad hoc Networks (MANETs), nonmobile networks, and other communication systems.
In a typical wireless network, the half-duplex constraint mandates that a given wireless device cannot transmit and receive simultaneously over the same frequency band. In the Open System Interconnection (OSI) model, this constraint is typically intrinsic to implementation of one or more of the lower layers, such as the physical layer and/or the data link layer—typically involving the Media Access Control (MAC) sublayer of the data link layer.
There have been numerous works on the design of MAC protocols for wireless ad hoc networks. Typically, the collision model is assumed, where if multiple users simultaneously transmit to the same user, their transmissions are lost due to collision at the receiver. Thus, state-of-the-art designs either apply ALOHA-type of random access scheme or schedule users orthogonally ahead of transmissions, or use a mixture of random access and scheduling/reservation. However, random access leads to poor efficiency (e.g., ALOHA's efficiency is generally no more than about 30%), while scheduling users is often difficult and subject to the hidden terminal and exposed terminal problems. Moreover, the fundamental constraint of half-duplex is that a terminal can only listen to the channel during its non-transmission (or silence) time slots. For example, if several users each have data to broadcast to other users, existing schemes allow only one user to succeed at a time, because if two users broadcast simultaneously, they fail to receive data from each other. The usual approach to the half-duplex constraint is to define a time-division protocol which determines a priori, a schedule for separating transmission slots and listening slots. There have been studies of achieving full duplex communication using two radios or two radio frequencies, but such convenience comes at the expense of reduced spectral efficiency. Thus, there remains a demand for further contributions in this area of technology.